Method for the preparation of perfluoroalkyl containing pyrazoles carboxylates

ABSTRACT

The present invention pertains to a novel process for the preparation of Fluoroalkylpyrazole- or Bisperfluoroalkypyrazole carboxylates comprising a cyclization of Perfluoroalkyl ketoesters with hydrazines.

The present invention pertains to a novel process for the preparation of Fluoroalkylpyrazole- or Bisperfluoroalkypyrazole carboxylates comprising a cyclization of Perfluoroalkyl ketoesters with hydrazines.

N-Allyl-3-Perfluoroalkyl-5-Fluoropyrazoles carboxylates are important intermediates for the preparation of agrochemical active ingredients, particularly of fungicides. Correspondingly, N-Alkyl-3-Perfluoroallcyl-5-Fluoropyrazoles carboxylates are described, for example, in the synthesis of fungicidally effective pyrazole carboxamides derivatives (cf e.g. WO 2010/130767), or in the synthesis of fungicidally effective arylalkylpyrazolecarboxamide derivatives and analogues (cf e.g. WO 2011/151370).

Usually, 3-Perfluoralkyl-5-Fluoro pyrazoles carboxylates are prepared via multistep transformations starting from acetoacetates. The preparative process of 5-fluoro-1-alkyl-3-fluoroalkyl-1H-pyrazole-4-carbonyl chlorides from 5-chloro-1-alkyl-3-fluoroallcyl-1H-pyrazol-4-carbaldehyde is disclosed in WO 2011/061205.

Proceeding from this prior art, the object of the present invention is to provide an improved one step process for the preparation of Fluoroalkylpyrazole- or Bisperfluoroalkypyrazole carboxylates derivatives which can be carried out easily and cost-effectively. The Fluoroalkylpyrazole- or Bisperfluoroalkypyrazole carboxylates obtainable using this desired process should preferably be obtained with high yield and high purity. In particular, the desired process should allow the desired target compounds to be obtained without the need for complex purification methods.

This object is achieved by a novel process for the preparation of Fluoroalkylpyrazole- or Bisperfluoroalkypyrazole carboxylates.

The present invention thus relates to a new process (A) for the preparation of pyrazole carboxylates of the formula (I)

in which R¹ is hydrogen, C₁-C₆ Alkyl, Aralkyl or Benzyl,

R² is C₁-C₅-Haloalkyl,

R³ is C₁-C₁₀ alkyl or C₁-C₁₀-Haloalkyl,

R⁴ is Cl, F, or C₁-C₅-Haloalkyl,

characterized in that Fluoroalkylacetoactates of formula (II)

in which R² and R³ are as defined above and

R⁵ is C₁-C₆-Haloalkyl,

are reacted with a hydrazine of the formula (III)

R¹—NHNH₂   (III)

in which R¹ is as defined above.

The process (A) according to the invention can be illustrated by the following formula scheme 1:

in which R¹, R², R³, R⁴ and R⁵ are as defined above.

The radical R¹ in these formula (III) and (I) preferably represents a hydrogen atom or C₁-C₅-Alkyl.

The radical R² in these formula (II) and (I) preferably represents HCF₂, CF₃ or C₂F₅, and more preferably HCF₂.

The radical R³ in these formula (II) and (I) preferably represents C₁-C₅-Alkyl.

The radical R⁴ in this formula (I) preferably represents F or C₁-C₅-Haloalkyl, and more preferably F or HCF₂.

The radical R⁵ in this formula (II) preferably represents CCl₂F, CF₃, CF₂Cl, CFCl₂, CF₂CF₃, CF₂CF₂H, more preferably represents CCl₂F, CF₃, CF₂CF₂H, and even more preferably represents CF₃.

Very particular preference is given to the use of the processes according to the invention for the preparation of the following compounds:

In which R³ is C₁-C₁₀ Alkyl or C₁-C₁₀-Haloalkyl, preferably C₁-C₅-Alkyl.

Some Ketoesters of the formula II (R²═CF₂H, R⁵═CF₃) are known (cf. Tetrahedron Letters, 2002 43(43), 7731-7734).

Direct trifluoromethylation of 1,3-dicarbonyl compounds (R² equals Alkyl) with CF₃I in the presence of a Fenton reagent (FeSO₄/H₂O₂) in dimethylsulfoxide is described in Tetrahedron Letters, 2012, 68(12), 2636-2649. 1,3-Diketones, 3-oxocarboxylates, and 3-oxocarboxamides were trifluoromethylated at the methylene carbon between two oxo groups. Cycloaddition of hydrazine derivatives and 2-(trifluoromethyl)-1,3-dicarbonyl compounds provided fluorinated pyrazoles.

Preparation of compounds with R² equals Haloalkyl is not described in the prior art and their utilization for the preparation of pyrazoles of the formula (I) is unknown.

It was now found that ketoster of the formula (II) can be used for the preparation of the pyrazoles of the formula (I) via reaction with hydrazines.

Two isomers of perfluoroalkylcontaining pyrazoles carboxylates (la and lb) could generally be formed when the cyclisation of ketoesters of formula (II) with hydrazines of formula (III) according to scheme lab is performed:

Surprisingly we found that only one isomer pyrazole (Ia) is formed when cyclisation is realized with substituted hydrazine. The reaction proceeds with the participation of the carbonyl function in position 2 and polyfluoralkyl group R⁵ in position 3. The fluoroalkygroup R² remains untouched.

According to a further embodiment of the present invention, the cyclisation step with hydrazine is performed in different solvents selected from alcohols, preferably methanol, ethanol, or isopropanol, nitriles, preferably acetonitrile, or butyronitrile, amides, preferably dimethylformamide, or dimethylacetamide, and organic acids, preferably formic acid or acetic acid. Most preferred solvents for the cyclisation are methanol and ethanol, acetic acid.

According to a further embodiment of the present invention, the cyclization is performed at a temperature ranging from 20 to 100° C., more preferably at a temperature ranging from 20° C. to 60° C., most preferably from 20° C. to 50° C.

The reaction time is generally not of critical importance and can depend on the reaction volume; preferably it is within the range of 1 to 5 h.

The ratio of the compound of formula (II) and (III) can vary within a large range; preferably it is within 0.9 and 1.5 equivalents, more preferably between 1 to 1.2 equivalents of hydrazine per one equivalent of the compound of formula (II).

The reaction can be performed in the presence of organic and inorganic bases. Preferred organic bases are: triethylamine, tripropylamine, tributylamin, methydiisopropylamin, N-methylmorpholine, pyridine, alkylpyridines.

Preferred inorganic bases to carry out the reaction are: NaHCO₃, K₂CO₃, NaOH, NaHCO₃.

The amount of base is selected between 1 and 3 equivalents, preferably between 1 and 2 equivalents, more preferably one equivalent of base for one equivalent of compound of formula (II).

The present invention also relates to the use Fluoroalkylacetoactates of formula (II)

in which R² is C₁-C₅- Haloalkyl, preferably HCF₂, CF₃ or C₂F₅ and more preferably HCF₂; R³ is C₁-C₁₀ Alkyl or C₁-C₁₀-Haloalkyl, preferably C₁-C₅Alkyl and R⁵ is C₁-C₆ Haloalkyl, preferably CCl₂F, CF₃, CF₂Cl, CFCl₂, CF₂CF₃ or CF₂CF₂H, more preferably it represents CCl₂F, CF₃, CF₂CF₂H, and even more preferably represents CF₃ for the preparation of pyrazole carboxylates of the formula (I)

in which R¹ is hydrogen, C₁-C₆ Alkyl, Aralkyl or Benzyl; preferably hydrogen or C₁-C₅ Alkyl; R² and R³ are as above defined; R⁴ is Cl, F, or C₁-C₅ Haloalkyl, preferably F or C₁-C₅-Haloalkyl, and more preferably F or HCF₂.

The present invention also provides a new process (B) for the preparation of fluoroalkylacetoactate derivatives of formula (II)

In which R², R³ and R⁵ are as defined above,

characterized in that haloderivatives of formula (IV)

in which R² and R³ are as described, above and Hal is halogen, are reacted with perfluoralkyl copper CuR⁵ in which R⁵ is as defined above.

The process (B) according to the invention can be illustrated by the following formula scheme 2:

in which R², R³ and R⁵ are as herein defined.

Haloderivatives of the formula (IV) are known or obtainable by known methods (Tetrahedron letters, 2009, 65(36), 7538-7552, Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1984, (5), 1106-14). The preparation of Ethyl 2-Bromo-4,4-difluor-3-oxobutyrcarboxylate is described in WO 2004/014847.

CuR⁵ can be prepared “ in situ” from Perfluoralkyliodide R⁵-I and Cu (US patent 3408411, Tetrahedron 1969,25, 5921).

CF₃Cu can be prepared from CF₃H and CuCl (see. Grushin et al, JACS 2011, 133, 20901), C₂F₅Cu from C₂F₅Si(Me)₃,CuCl and KF (Kobayashi et al Tetr. Letter 1969, 4095).

The Hal/R⁵ exchange proceeds in different solvents selected from DMF, DMA or Tetrahydrofurane, Acetonitrile, NMP, Dimethoxyethane or Diglym.

Most preferred solvents for the cyclisation are acetonitrile Acetonitrile, DMF, DMA, NMP.

According to a further embodiment of the present invention, the cyclization is performed at a temperature ranging from 20 to 130° C., more preferably at a temperature ranging from 20° C. to 100° C., most preferably from 20° C. to 80° C.

The reaction time is generally not of critical importance and can depend on the reaction volume, preferably it is within the range of 3 and 15 h.

The ratio of the compound of formula (IV) and CuR⁵ can vary within a large range, preferably it is within 0.9 and 2.5 equivalents, more preferably between 1 to 2 equivalents, and most preferably 1-1,5 equivalent of CuR⁵ per one equivalent of the compound of formula (IV).

The present invention also relates to the use of haloderivatives of formula (IV)

in which R² is C₁-C₅- Haloalkyl, preferably HCF₂, CF₃ or C₂F₅, more preferably HCF₂; R³ is C₁-C₁₀ Alkyl or C₁-C₁₀-Haloalkyl, preferably C₁-C₅-Alkyl,

Hal is Halogen,

for preparing fluoroalkylacetoactate derivatives of formula (II)

in which R² and R³ are as defined above and R⁵ is C₁-C₆-Haloalkyl, preferably CCl₂F, CF₃, CF₂Cl, CFCl₂, CF₂CF₃ or CF₂CF₂H, more preferably CCl₂F, CF₃, CF₂CF₂H, and even more preferably it represents CF₃.

The present invention also provides a new process (C) for the preparation of pyrazole carboxylates of the formula (I)

in which R¹, R², R³ and R⁴ are as defined herein, characterized in that, in a first step, haloderivatives of formula (IV)

in which R², R³ and Hal are as above defined, are reacted with perfluoralkyl copper CuR⁵ in which R⁵ is as above described to obtain fluoroalkylacetoactate derivatives of formula (II)

In which R², R³ and R⁵ are as above defined,

and the resulting fluoroalkylacetoactate derivatives of formula (II)

In which R², R³ and R⁵ are as above defined,

are reacted with hydrazines of the formula (III)

R¹—NHNH₂   (III)

In which R¹ is as above defined.

The process (C) according to the invention can be illustrated by the following formula scheme 3:

in which R¹, R², R³, R⁴ , R⁵ and Hal are as herein defined.

The present invention further relates to processes as herein described for the preparation of pyrazole carboxylates of the formula (I) selected among compounds of formula (Ic) or (Id)

in which R³ is C₁-C₁₀-Alkyl or C₁-C₁₀-Haloalkyl, preferably C₁-C₅-Alkyl.

In connection with the present invention, the term halogen (X or Hal) comprises, unless otherwise defined, those elements which are chosen from the group consisting of fluorine, chlorine, bromine and iodine; fluorine, chlorine and bromine being preferably used and fluorine and chlorine being particularly preferably used.

Appropriately substituted groups can be mono- or polysubstituted, it being possible for the substituents in polysubstitutions to be identical or different.

Alkyl groups substituted with one or more halogen atoms (—X or -Hal) are chosen, for example, from trifluoromethyl (CF₃), difluoromethyl (CHF₂), CF₃CH₂, C₂F₅, ClCH₂, CF₂CF₂H, CF₃CCl₂ and CHF₂CCl₂.

Allyl groups in connection with the present invention are, unless otherwise defined, linear, branched or cyclic hydrocarbon groups which can optionally exhibit one, two or more heteroatoms chosen from oxygen, nitrogen, phosphorus and sulphur. In addition, the alkyl groups according to the invention can optionally be substituted by additional groups chosen from —R′, halogen (X), alkoxy (OR′), thioether or mercapto (SR′), amino (NR′₂), silyl (SiR′₃), carboxyl (COOR′), cyano (CN), acyl (—(C═O)R′) and amide (—CONR′₂) groups, R′ being hydrogen or a C₁-C₁₂-alkyl group, preferably a C₂-C₁₀-alkyl group, particularly preferably a C₃-C₈-alkyl group, which can exhibit one or more heteroatoms chosen from nitrogen, oxygen, phosphorus and sulphur.

The definition C₁-C₁₂-alkyl comprises the biggest range defined herein for an alkyl group. Specifically, this definition comprises, for example, the meanings methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and t-butyl, n-pentyl, n-hexyl, 1,3-dimethylbutyl, 3,3 dimethylbutyl, n-heptyl, n-nonyl, n-decyl, n-undecyl and n-dodecyl.

The definition cyclic C₃-C₁₂-alkyl groups comprises the biggest range defined herein for a cyclic alkyl group. Specifically, this definition comprises, for example, the meanings cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl.

Alkenyl groups in connection with the present invention are, unless otherwise defined, linear, branched or cyclic hydrocarbon groups which comprise at least one single unsaturation (double bond) and can optionally exhibit one, two or more single or double unsaturations or one, two or more heteroatoms chosen from oxygen, nitrogen, phosphorous and sulphur. In addition, the alkenyl groups according to the invention can optionally be substituted by additional groups chosen from —R′, halogen (X), alkoxy (OR′), thioether or mercapto (SR′), amino (NR′₂), silyl (SiR′₃), carboxyl (COOR′), cyano (CN), acyl (—(C═O)R′) and amide (—CONR′₂) groups, R′ being hydrogen or a C₁-₁₂-alkyl group, preferably a C₂-₁₀-alkyl group, particularly preferably a C₃-₈-alkyl group, which can exhibit one or more heteroatoms chosen from nitrogen, oxygen, phosphorous and sulphur.

The definition C₂-C₁₂-alkenyl comprises the biggest range defined herein for an alkenyl group. Specifically, this definition comprises, for example, the meanings vinyl; allyl (2-propenyl), isopropenyl (1-methylethenyl); but-1-enyl (crotyl), but-2-enyl, but-3-enyl; hex-1-enyl, hex-2-enyl, hex-3-enyl, hex-4-enyl, hex-5-enyl; hept-1-enyl, hept-2-enyl, hept-3-enyl, hept-4-enyl, hept-5-enyl, hept-6-enyl; oct-1-enyl, oct-2-enyl, oct-3-enyl, oct-4-enyl, oct-5-enyl, oct-6-enyl, oct-7-enyl; non-1-enyl, non-2-enyl, non-3-enyl, non-4-enyl, non-5-enyl, non-6-enyl, non-7-enyl, non-8-enyl; dec-1-enyl, dec-2-enyl, dec-3-enyl, dec-4-enyl, dec-5-enyl, dec-6-enyl, dec-7-enyl, dec-8-enyl, dec-9-enyl; undec-1-enyl, undec-2-enyl, undec-3-enyl, undec-4-enyl, undec-5-enyl, undec-6-enyl, undec-7-enyl, undec-8-enyl, undec-9-enyl, undec-10-enyl; dodec-1-enyl, dodec-2-enyl, dodec-3-enyl, dodec-4-enyl, dodec-5-enyl, dodec-6-enyl, dodec-7-enyl, dodec-8-enyl, dodec-9-enyl, dodec-10-enyl, dodec-11-enyl; buta 1,3dienyl, penta-1,3-dienyl.

Alkynyl groups in connection with the present invention are, unless otherwise defined, linear, branched or cyclic hydrocarbon groups which comprise at least one double unsaturation (triple bond) and can optionally exhibit one, two or more single or double unsaturations or one, two or more heteroatoms chosen from oxygen, nitrogen, phosphorous and sulphur. In addition, the alkynyl groups according to the invention can optionally be substituted by additional groups chosen from —R′, halogen (X), alkoxy (OR′), thioether or mercapto (SR′), amino (NR′₂), silyl (SiR′₃), carboxyl (COOR′), cyano (CN), acyl (—(C═O)R′) and amide (—CONR′2) groups, R′ being hydrogen or a linear, branched or cyclic C₁-₁₂-alkyl group which can exhibit one or more heteroatoms chosen from nitrogen, oxygen, phosphorous and sulphur.

The definition C₂-C₁₂-alkynyl comprises the biggest range defined herein for an alkynyl group. Specifically, this definition comprises, for example, the meanings ethynyl (acetylenyl); prop-1-ynyl and prop-2-ynyl.

Aryl groups in connection with the present invention are, unless otherwise defined, aromatic hydrocarbon groups which can exhibit one, two or more heteroatoms chosen from oxygen, nitrogen, phosphorous and sulphur and can optionally be substituted by additional groups chosen from —R′, halogen (X), alkoxy (OR′), thioether or mercapto (SR′), amino (NR′₂), silyl (SiR′₃), carboxyl (COOR′), cyano (CN), acyl (—(C═O)R′) and amide (—CONR₂′) groups, R′ being hydrogen or a C₁-₁₂-alkyl group, preferably a C₂-₁₀-alkyl group, particularly preferably a C₃-₈-alkyl group, which can exhibit one or more heteroatoms chosen from nitrogen, oxygen, phosphorous and sulphur.

The definition C₅-C₁₈-aryl comprises the biggest range defined herein for an aryl group having 5 to 18 atoms.

Specifically, this definition comprises, for example, the meanings cyclopenta-idienyl, phenyl, cycloheptatrienyl, cyclooctatetraenyl, naphthyl and anthracenyl.

The definition C₅-C₁₈-aryl groups exhibiting one, two or more heteroatoms chosen from oxygen, nitrogen, phosphorous and sulphur are chosen, for example, from the group consisting of 2 furyl, 3-furyl, 2-thienyl, 3-thienyl, 2-pyrrolyl, 3-pyrrolyl, 3-isoxazolyl, 4-isoxazolyl, 3-isothiazolyl, 4-isothiazolyl, 5-isothiazolyl, 3-pyrazolyl, 4-pyrazolyl, 5-pyrazolyl, 2 oxazolyl, 4-oxazolyl, 5-oxazolyl, 2-thiazolyl, 4-thiazolyl, 5-thiazolyl, 2-imidazolyl, 4 imidazolyl, 1,2,4-oxadiazol-3-yl, 1,2,4-oxadiazol-5-yl, 1,2,4-thiadiazol-3-yl, 1,2,4-thiadiazol-5-yl, 1,2,4-triazol-3-yl, 1,3,4-oxadiazol-2-yl, 1,3,4-thiadiazol-2-yl and 1,3,4-triazol-2-yl; 1pyrrolyl, 1-pyrazolyl, 1,2,4 -triazol-1-yl, 1-imidazolyl, 1,2,3-triazol-1-yl, 1,3,4-triazol-1-yl; 3pyridazinyl, 4-pyridazinyl, 2-pyrimidinyl, 4-pyrimidinyl, 5-pyrimidinyl, 2-pyrazinyl, 1,3,5triazin-2-yl and 1,2,4-triazin-3-yl.

Arylalkyl groups (aralkyl groups) in connection with the present invention are, unless otherwise defined, alkyl groups substituted by aryl groups which can exhibit a C₁-₈-alkylene chain and can be substituted in the aryl backbone or the alkylene chain by one or more heteroatoms chosen from oxygen, nitrogen, phosphorous and sulphur and optionally by additional groups chosen from —R′, halogen (X), alkoxy (OR′), thioether or mercapto (SR′), amino (NR′₂), silyl (SiR′₃), carboxyl (COOR′), cyano (CN), acyl (—(C═O)R′) and amide (—CONR′₂) groups, R′ being hydrogen or a C₁₋₁₂-alkyl group, preferably a C₂₋₁₀-alkyl group, particularly preferably a C₃₋₈-alkyl group, which can exhibit one or more heteroatoms chosen from nitrogen, oxygen, phosphorous and sulphur.

The definition C₇-C₁₉-aralkyl group comprises the biggest range defined herein for an arylalkyl group with a total of 7 to 19 atoms in the backbone and alkylene chain. Preference is given to those C₇-C₁₉-aralkyl groups comprising 5 or 6 carbon atoms or heteroatoms in the aryl backbone and 1 to 8 carbon atoms in the alkylene chain. Specifically, this definition comprises, for example, the meanings benzyl and phenylethyl.

Alkylaryl groups (alkaryl groups) in connection with the present invention are, unless otherwise defined, aryl groups substituted by alkyl groups which can exhibit a C₁-C₈-alkylene chain and can be substituted in the aryl backbone or the alkylene chain by one or more heteroatoms chosen from oxygen, nitrogen, phosphorous and sulphur and optionally by additional groups chosen from —R′, halogen (X), alkoxy (OR′), thioether or mercapto (SR′), amino (NR′₂), silyl (SiR′₃), carboxyl (COOR′), cyano (CN), acyl (—(C═O)R′) and amide (CONR′₂) groups, R′ being hydrogen or a C₁-C₁₂-alkyl group, preferably a C₂-C₁₀-alkyl group, particularly preferably a C₃-C₈-alkyl group, which can exhibit one or more heteroatoms chosen from nitrogen, oxygen, phosphorous and sulphur.

The definition C₇-C₁₉-alkylaryl group comprises the biggest range defined herein for an alkylaryl group with a total of 7 to 19 atoms in the backbone and alkylene chain. Preference is given to those C₇-C₁₉-aralkyl groups comprising 5 or 6 carbon atoms or heteroatoms in the aryl backbone and 1 to 8 carbon atoms in the alkylene chain. Specifically, this definition comprises, for example, the meanings tolyl-, 2,3-, 2,4-, 2,5-, 2,6-, 3,4- or 3,5-dimethylphenyl.

The alkyl, alkenyl, alkynyl, aryl, alkylaryl and aralkyl groups can furthermore exhibit one or more heteroatoms which, unless otherwise defined, are chosen from nitrogen, oxygen, phosphorous and sulphur. The heteroatoms in this connection replace the carbon atoms indicated.

The compounds according to the invention can exist, if appropriate, as mixtures of different possible isomeric forms, in particular of stereoisomers, such as, e.g., E and Z isomers, threo and erythro isomers, and optical isomers, but, if appropriate, also tautomers. Both the E and Z isomers, as also the threo and erythro isomers, and also the optical isomers, any mixture of these isomers, and the possible tautomeric forms, are disclosed and claimed.

EXAMPLES Example 1 4,4-difluoro-3-oxo-2-(trifluoromethyl)butatioate

Ethyl 4,4-difluoro-3-oxo-2-butanoate 40 g (241 nunol) was dissolved in 600 ml DMSO and water solution of FeSO₄ (723 mmol) was added while the temperature was kept below 40° C. 98 g of CF₃1 was added in a slow stream of gas while at the same time H₂O₂ (35 o solution in water, 482. mmol) as added slowly within 15 min The mixture was cooled du icing the addition. The mixture was stirred at room temperature for 30 min. The conversion of the Ethyl 4,4-ditluoro-3-oxo-2-butanoate was found to be 86%. The mixture was poured carefully into 1.5 L of water under cooling. The product was exptracted with Methylter.tbutylether, washed with with water and brine and dried over Na₂SO₄.

The solvent was removed to give 48 g of the product (as a mixture with hydrate) with purity of 90% as a mixture of two compounds.

¹H NMR (CDCl3) (t, 3H); 4.4 (q, CH2); 4.7 (q, 1H, 9 Hz), 5.9 (t, 1H, 48 Hz) ppm.

¹⁹F NMR (CDCl3); 63.5 (d, 3F ). 126.9 (3′t, 3F) ppm.

¹³C NMR (CDCl3):

Example 2 4,4-difluoro-3-oxo-2-(trifluoromethyl)butatioate

24.5 g of ethyl 2-bromo-4,4-difluoro-3-oxobutanoate (prepared according and CuCF₃ prepared from (CF₃H according to the procedure described in JACS. 2011, 133, 20901-20913) were mixed together in 40 ml CH₃CN and the mixture stirred for 10 h at 40° C. GC showed the full conversion and the formation of the desired product. The mixture was cooled and poured on 500 ml of ice water The product was extracted with Methylter.tbutylether, washed with with water and brine and dried over Na₂SO₄.

The solvent was removed to give 20 g of the product with purity of 90%. The product was used without purification for the next step.

Example 3 Ethyl 1-Methyl-3-clifluoromethyl-5-fluoro-1H-pyrazolcarboxylate

2.34 g (0.01 mol) of ethyl 4,4-difluoro-3-oxo-2-(trifluoromethyl)butanoate, and 0.46 g methylhydrazin were mixed together in 10 ml acetonitrile. Reaction mixture was kept 5 h at 30° C. The solvent was removed in vacuuo and the product was isolated via column chroniatografie on SiO₂ using Ethylacetate hexane. Yield 58%.

Mass spectra (ESPI) positive m/z 223.

¹H NMR: 1.2/t, 3H); 3.6 (s, 3H), 4.16 (q, 2H); 6.92 (t, 1H)

¹H NMR: 1.2/t, 3H); 3.6 (s,3H); 4.16 (q, 2H); 6.92 (t, 1H).

¹³C NMR (CD3CN):

Example 4 Ethyl 1-phenyl1-3-difluoromethyl-5-fluoro-1H-pyrazolcarboxylate

Similar prepared from 4,4-difluoro-3-oxo-2-(trifluoromethypbutarioate and phenylhydrazine.

Yield 63%.

¹³C NMR (CDCl3). 

1. Process for preparing a pyrazole carboxylate of formula (I)

in which R¹ is hydrogen, C₁-C₆ Alkyl, Aralkyl or Benzyl; R² is C₁-C₅-Haloalkyl, R³ is C₁-C₁₀-Alkyl or C₁-C₁₀-Haloalkyl, R⁴ is Cl, F, or C₁-C₅-Haloalkyl, wherein a Fluoroalkylacetoactate of formula (II)

in which R² and R³ are as defined above, and R⁵ is C₁-C₆ Haloalkyl, is reacted with a hydrazine of formula (III) R¹—NHNH₂   (III) in which R¹ is as defined above.
 2. A Fluoroalkylacetoactate of formula (II)

in which R² is C₁-C₅-Haloalkyl, R³ is C₁-C₁₀-Alkyl or C₁-C₁₀-Haloalkyl, R⁵ is C₁-C₆-Haloalkyl, capable of being used for preparing a pyrazole carboxylate of formula (I)

in which R¹ is hydrogen, C₁-C₆-Alkyl, Aralkyl or Benzyl; R² and R³ are as above defined; R⁴ is Cl, F, or C₁-C₅-Haloalkyl
 3. A fluoroalkylacetoactate according to claim 2 wherein R² is HCF₂, R³ is C₁-C₅Alkyl and R⁵ is CF₃.
 4. Process for preparing a fluoroalkylacetoactate derivative of formula (II)

in which R² is C₁-C₅-Haloalkyl, R³ is C₁-C₁₀-Alkyl or C₁-C₁₀-Haloalkyl, R⁵ is C₁-C₆-Haloalkyl, comprising reacting a haloderivative of formula (IV)

in which R², R³ are as above described, and Hal is halogen; with perfluoralkyl copper CuR⁵ in which R⁵ is as above described.
 5. Process according to claim 4 wherein R² is HCF₂, R³ is C₁-C₅-Alkyl and R⁵ is CF₃.
 6. A haloderivative of formula (IV)

in which R² is C₁-C₅-Haloalkyl, R³ is C₁-C₁₀-Alkyl or C₁-C₁₀-Haloalkyl, Hal is halogen, capable of being used for preparing a fluoroalkylacetoactate derivative of formula (II)

in which R² and R³ are as defined above and R⁵ is C₁-C₆-Haloalkyl,
 7. A haloderivative according to claim 6 wherein R² is HCF₂, R³ is C₁-C₅-Alkyl and R⁵ is CF₃.
 8. Process for preparing a pyrazole carboxylate of formula (I)

in which R¹ is hydrogen, C₁-C₆-Alkyl, Aralkyl or Benzyl; R² is C₁-C₅-Haloalkyl, R³ is C₁-C₁₀-Alkyl or C₁-C₁₀-Haloalkyl, R⁴ is Cl, F, or C₁-C₅ Haloalkyl, wherein, a haloderivative of formula (IV

in which R² and R³ are as above defined, and Hal is halogen, is reacted with perfluoralkyl copper CuR⁵ in which R⁵ is C₁-C₆ Haloalkyl, to obtain a fluoroalkylacetoactate derivative of formula (II)

In which R², R³ and R⁵ are as above defined, and the resulting fluoroalkylacetoactate derivative of formula (II)

in which R², R³ and R⁵ are as above defined, is reacted with a hydrazine of formula (III) R¹—NHNH₂   (III) in which R¹ is as above defined.
 9. Process according to claim 1 wherein the pyrazole carboxylate of formula (I) is selected among compounds of formula (Ic) or (Id)

in which R³ is C₁-C₁₀-Alkyl or C₁-C₁₀-Haloalkyl. 